1. Field of the Invention
The present invention relates to a magnetoresistive (MR) effect element which detects an external magnetic field such as a signal magnetic field and exhibits variations in resistance responsive to the intensity of the magnetic field, a thin-film magnetic head including the MR effect element, a head gimbal assembly (HGA) including the thin-film magnetic head, and a magnetic disk drive apparatus including the HGA. The present invention also relates to a method for manufacturing a thin-film magnetic head including such MR effect element.
2. Description of the Related Art
As magnetic disk drive apparatuses increase in capacity and reduce in size, thin-film magnetic heads having an MR effect element with the giant magnetoresistive (GMR) effect and tunnel magnetoresistive (TMR) effect are being intensively developed in quest to provide highly sensitive and high-output thin-film magnetic heads.
The structures of the MR effect element are broadly classified into two types. One is the current-in-plane (CIP) structure in which sense current flows in parallel with the layer planes of an MR effect multilayer; the other is the current perpendicular-to-plane (CPP) structure in which an MR effect multilayer is sandwiched between upper and lower electrode layers and sense current flows in a direction perpendicular to the layer planes of the multiplayer. The CPP structure is also used in GMR heads as well as TMR heads today as disclosed in Japanese Patent Publication No. 05-275769A, for example. CPP-GMR heads that have a spin valve multiplayer film (including specular-type magnetic multilayer film and dual-spin-valve magnetic multilayer film), like CIP-GMR heads, have also been developed.
The CPP structure uses a magnetic shield layer itself as an electrode and, unlike the CIP structure, does not require an insulating layer between the magnetic shield layer and the MR effect multilayer. Therefore, the CPP structure is more suitable than the CIP structure for narrower read gaps that accommodate ever increasing recording density. Furthermore, the CPP structure is capable of providing higher output from narrow track widths as compared with the CIP structure. Thus, advantageously, the CPP structure has a higher potential to keep pace with increasing recording densities than the CIP structure.
Although the CPP structure is suitable for high recording density, the CPP structure has a problem that reattachments left on the side surface of the MR effect multilayer during formation of the CPP structure acts as parallel paths through which sense current can flow, thereby reducing reading output.
The CPP structure, in which sense current flows between upper and lower electrode layers in a direction perpendicular to the layer planes of the MR effect multilayer, has a magneto-sensitive portion that includes a pinned layer, a non-magnetic intermediate layer, and a free layer, senses a magnetic field and relates to the output. If a reattachment remains on a side surface of the magneto-sensitive portion, a current path parallel with the magneto-sensitive portion is formed, and a sense current diverts through the parallel path, even in the case of the same resistance change by a signal magnetic field, which reduces the output.
FIGS. 10a and 10b show cross-sectional views of an MR effect multilayer for illustrating how such a reattachment is formed. A cross-section of an MR effect multilayer 1100 after patterning using ion milling typically has regions 1105 and 1106 as shown in FIG. 10a. A reattachment on a steeply sloping side surface of the region 1105 is harder to remove during etching using such a method as ion milling than on the side surface of the region 1106. One reason for this is that the reattachment 1104 deposited on a resist 1101 formed on the MR effect multiplayer 1100 as a mask blocks part of ion beam that would reach the side surface of the region 1105 to inhibit the reattachment on the region 1105 from being etched.
To avoid the influence of reattachments, the magneto-sensitive portion may be provided in a position 1103 in the region 1106 where reattachments can be easily removed. However, if the magneto-sensitive portion is provided in the position 1103, the width of the magneto-sensitive portion along the track-width direction is widened as compared with the case where it is provided in a position 1102 in the region 1105, making it difficult to accommodate high recording density. Furthermore, as shown in FIG. 10b, the distance d1103 between the free layer in the magneto-sensitive portion and a bias layer such as a hard bias layer provided on both sides of the magneto-sensitive portion is increased as compared with the distance d1102, which is disadvantageous in terms of the stability of the magnetic domain in the free layer.